The goal of the Children's Hospital of Philadelphia (CHOP) NICHD-sponsored Institutional Ruth L. Kirschstein National Research Service Award (NRSA) is to increase the number and effectiveness of subspecialty pediatricians with rigorous training in basic, translational, and clinical research. We accomplish this goal by training outstanding pediatric fellows to become successful physician-scientists, addressing questions of fundamental importance to health and disease in children. Candidates for our program are enrolled in our subspecialty fellowship programs and are identified through national searches for the best and the brightest, with aggressive diversity recruitment. Each candidate identifies a prospective mentor from a large group of mentors at CHOP and at the University of Pennsylvania (Penn). These CHOP-T32-NRSA mentors were selected based on the following criteria: rigorous science in areas germaine to pediatrics, a record of successful mentoring and collaboration, a strong record of extramural funding, and programmatic balance. Trainee progress is reviewed twice a year by our Internal Advisory Committee. Trainees are supported for two years to conduct research as outlined in their formal proposals. Trainees in clinical investigation pursue a master's degree in one of several available programs, and trainees in basic and translational research have access to a wide variety of outstanding mentors and educational opportunities, all supported by a wide array of clinical and laboratory research cores. Our T32-NRSA and the companion K12- CHRCDA grant have been highly successful in training physician-scientists who are capable of conducting independent research and who have consistently assumed academic positions. This renewal of our CHOP-T32-NRSA will continue the tradition established during the first 12 years of this grant, taking advantage of the tremendous strengths of CHOP as an academic pediatric institution with an outstanding pool of subspecialty fellows, a large number of experienced mentors, and cutting edge research programs. CHOP and Penn provide a comprehensive, well- supported and resource-intense environment, as well as a proven track record of training academic investigators in basic, translational, and clinical research. The training of physician-scientists in pediatric subspecialties is critical for advancing the understanding and treatment of childhood diseases, and for providing future leaders in academic medicine.